I would try placing a silverwood sapling down by your base and traveling in a large circular area around your base and discover several of the nodes around you. Now, this shouldn't allow the silverwood tree to grow since it needs 100 vis but it worked for me. You could also drag the nearest node but that could take awhile. As an alternative to that and as kind of a quick fix I would plant silverwood saplings in a line from the nearest node about 30 blocks apart and grow them with the hoe of growth from farthest to closest. You could worry about combining those nodes later to make everything pretty.